In producing photographic images, a typical approach is to coat onto one or both major surfaces of a planar support a radiation-sensitive material capable of, alone or in combination with other image-forming materials, undergoing a change in optical density as a function of exposure and/or photographic processing. Coating in this way can result in loss (i.e., reduction) of image definition by reason of lateral image spreading--that is, spreading in a direction parallel to the major surfaces of the support. Lateral image spreading can be the result of radiation scattering during exposure--e.g., halation--or lateral reactant migration during photographic processing. The effects of lateral image spreading can be analyzed mathematically in terms such as modulation transfer function, or lateral image spreading can be discussed in sensory terms, such as graininess, which is recognized to be both a function of image definition loss and the randomness of image definition loss. Graininess is particularly a problem in silver halide photography, since it is directly related to and limits in many instances attainable photographic speeds.
Typical approaches to reducing graininess in photographic images have involved some modification of the imaging layers of photographic elements, their mode of processing or modification of the layers after an image has been produced therein. An illustrative teaching of this type is that of U.K. Pat. No. 1,318,371, which recognizes graininess to be a function of the randomness of image distribution and therefore teaches to superimpose on the imaging layer a grid which subdivides the image, either before or after its formation. In every embodiment of that patent planar photographic support surfaces are coated.
Except on a macro scale, which has no relevance to graininess, in only a few instances have photographic element support surfaces been employed for imaging materials which depart from a planar form. One such approach is the Aluphoto process in which silver halide is formed in situ in the random pores of an anodized aluminum plate, illustrated by Wainer, "The Aluophoto Plate and Process", 1951 Photographic Engineering, Vol. 2, No. 3, pp. 161-169. Kumasaka U.S. Pat. Nos. 3,776,734 and 4,092,169 are essentially cumulative. Chiba et al U.S. Pat. No. 3,779,775 applies the teachings of in situ formation of silver halide in random pores to polymeric support materials. Ohyama et al U.S. Pat. No. 3,214,274 uses random pores in subbing layers to anchor layers to photographic supports. Nonplanar supports intended to level out overlapping emulsion coating patterns are disclosed by Rogers U.S. Pat. Nos. 2,983,606 and 3,019,124.
Land U.S. Pat. No. 3,138,459 teaches the use of a two-color screen, wherein two additive primary filter dyes are coated into grooves on opposite sides of a transparent support. The grooves on one side of the support are interposed between grooves on the opposite side of the support. The grooves prevent lateral spreading of the filter dyes into overlapping relationship. However, to accomplish this the grooves on one major surface of the support must be laterally spaced by a distance greater than their width. Dufay U.K. Pat. No. 15,027 (1912) discloses a four color screen in which grooves on opposite major surfaces overlap.
Carlson U.S. Pat. No. 2,599,542 has taught that either randomly or regularly spaced recesses or projections can be employed in xerographic plates to obtain half-tone images. However, xerographic photoconductive coatings, by reason of their electrical biasing, exhibit no significant halation on exposure, and Carlson does not alter the optical density of the photoconductive layer during processing.
The retention of ink in recesses in gravure printing elements is well known. Weigl U.S. Pat. No. 3,561,358 applies elements having initially uniform cells to gravure printing.